Method for manufacturing an optoelectronic device with self-aligning light confinement walls

ABSTRACT

There is described an optoelectronic device where each light-emitting diode has a wire-like shape. Spacing walls are formed so that the lateral sidewalls of each light-emitting diode are surrounded by at least one of the spacing walls. Light confinement walls directly cover the lateral sidewalls of the spacing walls by being in contact with the latter. The spacing walls have a convex-shaped outer face. At least one of the spacing walls has, over a lower portion, a thickness that increases when getting away from the substrate. They have, over an upper portion, a thickness that decreases at the level of the upper border of the light-emitting diode when getting away from the substrate. The light confinement walls have an inner face having a concave shape matching with the convex shape and directed towards the light-emitting diode for which it confines the light radiation thereof.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of PCT Application No.PCT/FR2019/051502 filed on Jun. 19, 2019, which claims priority toFrench Patent Application No. 18/55401 filed on Jun. 19, 2018, thecontents each of which are incorporated herein by reference thereto.

TECHNICAL FIELD

The present invention concerns a method for manufacturing anoptoelectronic device including an array of light-emitting diodes,including the following steps:

-   -   formation of the array of light-emitting diodes on a support        face of a substrate, this step being carried out so that each        light-emitting diode has an elongate wire-like shape according        to a longitudinal axis extending according to a transverse        direction of the optoelectronic device directed transversely to        the support face of the substrate,    -   formation of spacing walls made of a first dielectric material        transparent to the light radiation originating from the        light-emitting diodes, the formed spacing walls being such that        the lateral sidewalls of each light-emitting diode, over the        entire height thereof considered according to the transverse        direction, are surrounded by at least one of the spacing walls,    -   formation of light confinement walls made of a second material        adapted to block the light radiation originating from the        light-emitting diodes, the formed light confinement walls        directly covering the lateral sidewalls of the spacing walls by        being in contact with the latter, so that the light radiation        originating from each light-emitting diode and directed in the        direction of the adjacent light-emitting diodes is blocked by        the light confinement wall which covers the spacing wall that        surrounds said light-emitting diode.

The invention also concerns an optoelectronic device comprising:

-   -   an array of light-emitting diodes where each light-emitting        diode has an elongate wire-like shape according to a        longitudinal axis extending according to a transverse direction        of the optoelectronic device,    -   spacing walls made of a first dielectric material transparent to        the light radiation originating from the light-emitting diodes        and arranged such that the lateral sidewalls of each        light-emitting diode, over the entire height thereof considered        according to the transverse direction, are surrounded by at        least one of the spacing walls,    -   and light confinement walls made of a second material adapted to        block the light radiation originating from the light-emitting        diodes, the light confinement walls directly covering the        lateral sidewalls of the spacing walls by being in contact with        the latter, the light radiation originating from each        light-emitting diode and directed in the direction of the        adjacent light-emitting diodes being blocked by the light        confinement wall which covers the spacing wall that surrounds        said light-emitting diode.

The invention finds application in particular in display screens orimages projection systems.

BACKGROUND

By optoelectronic device, it should be understood herein a deviceadapted to perform the conversion of an electrical signal into anelectromagnetic radiation to be emitted, in particular light.

There are optoelectronic devices including light-emitting diodes, alsoknown under the acronym LED, formed on a substrate.

It is known that each light-emitting diode comprises an active materialexploiting quantum wells, a semiconductor portion doped according to afirst doping type to serve as a P-doped junction and a semiconductorportion doped according to a second doping type to serve as an N-dopedjunction.

Each light-emitting diode may be formed based on semiconductorthree-dimensional elements which, in turn, are at least partiallyobtained by epitaxial growth. The light-emitting diodes are typicallyformed based on a semiconductor material comprising for example elementsfrom the column III and column V of the periodic table of elements, suchas a III-V compound, in particular gallium nitride (GaN), indium andgallium nitride (InGaN) or aluminum and gallium nitride (AlGaN).

There are optoelectronic devices including an array of light-emittingdiodes having a determined emission surface throughout which istransmitted the light radiation emitted by the light-emitting diodes. Inparticular, such optoelectronic devices may be used in the making ofdisplay screens or images projection systems, where the array oflight-emitting diodes actually defines an array of light pixels whereeach pixel includes one or several light-emitting diode(s).

One of the difficulties relates to how to ensure that the lightradiation emitted by a light-emitting diode does not mix with the lightradiation emitted by the adjacent light-emitting diodes in order toimprove contrasts. In particular, one problem is how to ensure thatdiaphotic colors excitations between the sub-pixels are avoided, whichphenomenon is also known by the name «cross-talk» in the consideredtechnical field. Yet, this problem turns out to be even more difficultto solve given the ever-increasing miniaturization of the light-emittingdiodes.

A known solution consists in forming light confinement walls adapted toblock the transmission of the light radiation emitted by one or severalgiven light-emitting diode(s) towards one or several adjacentlight-emitting diode(s).

A known technique for forming such light confinement walls consists indepositing a resin layer over the light-emitting diodes, the resin beingphotolithographed while complying with a pattern guaranteeing thepresence of trenches intended to be filled afterwards with a material,for example through a growth or deposition technique, adapted to blockthe light radiation and even ensure a reflection of the latter

This technique has the drawback that it is difficult to follow anaccurate alignment between the confinement walls and the light-emittingdiodes. This problem is even more severe given the ever-increasingminiaturization of the light-emitting diodes in order to ultimatelyachieve a high resolution.

The document FR3000298A1 describes a solution in which a negative resinthat is photosensitive in the emission wavelengths range of thephotoconductor nanowires is deposited by covering the nanowires. Withthis negative resin type, in the exposed areas, the photons react withthe photosensitive negative resin and degrade the solubility propertiesthereof, the resin becoming less soluble. Afterwards, selective patternsmay be uncovered in a developer (typically a basic aqueous solution);indeed, the areas of the resin that are less soluble in the developerthus subsist at the surface of the substrate, the remainder beingsolubilized in the developer. The resin may be selected so as to becapable of self-conforming, that is to say conforming the closest to theshape of the nanowires. The self-conformation of the resin allowsleaving gaps between two adjacent nanowires. Then, it is proceeded witha step of depositing an ink into said gaps, thereby allowing definingadsorbent patterns of an adsorbent material in the sensitivitywavelengths range of the nanowires. Then, the nanowires are activated bycurrent injection from control pads. It is the illumination generated bythe nanowires which allows achieving the insulation, or not, of thedifferent portions within the resin. The interest of the adsorbent ink,and thus of the patterns in the gaps, relates to the fact that the resinthat encapsulates a defective nanowire is prevented from beingilluminated by a contiguous nanowire. Then, a step is implemented duringwhich the resin is developed at the level of the defective nanowires,leaving areas that are made less soluble and surrounding only the activenanowires. Then, the conductive layer that is present on top of thedefective nanowires is removed.

But this solution, given the steps and techniques required thereby, isnot yet optimal and is not fully satisfactory. It is complex toimplement, expensive, and remains restrictive with regards to the usedtechniques and materials.

Besides, the techniques that are currently implemented do not allowachieving enough collimation of the emitted light for some applications.In particular, they do not allow obtaining a satisfactory light beamopening. This is true especially in the case of wire-like shapedlight-emitting diodes which, nevertheless, still have many advantages.

In this context, there is a need to provide a method for manufacturingan optoelectronic device that is simple, effective and allowingincreasing the resolution while optimizing the contrast.

BRIEF SUMMARY

The present invention aims at providing a manufacturing method formanufacturing an optoelectronic device comprising an array oflight-emitting diodes which allows obtaining high-resolution andhigh-contrast optoelectronic devices in a simple, economical, effectiveand non-limiting way, while allowing obtaining a very good collimationof the light emitted by the light-emitting diodes.

This object can be achieved thanks to the implementation of a method formanufacturing an optoelectronic device including an array oflight-emitting diodes, including the following steps:

-   -   formation of the array of light-emitting diodes on a support        face of a substrate, this step being carried out so that each        light-emitting diode has an elongate wire-like shape according        to a longitudinal axis extending according to a transverse        direction of the optoelectronic device directed transversely to        the support face of the substrate,    -   formation of spacing walls made of a first dielectric material        transparent to the light radiation originating from the        light-emitting diodes, the formed spacing walls being such that        the lateral sidewalls of each light-emitting diode, over the        entire height thereof considered according to the transverse        direction, are surrounded by at least one of the spacing walls,    -   formation of light confinement walls made of a second material        adapted to block the light radiation originating from the        light-emitting diodes, the formed light confinement walls        directly covering the lateral sidewalls of the spacing walls by        being in contact with the latter, so that the light radiation        originating from each light-emitting diode and directed in the        direction of the adjacent light-emitting diodes is blocked by        the light confinement wall which covers the spacing wall that        surrounds said light-emitting diode,

wherein the step of forming the spacing walls is implemented so that theformed spacing walls have a convex-shaped outer face and so that atleast one of said spacing walls has, over a lower portion of the heightthereof considered according to the transverse direction located on theside of the support face of the substrate, a thickness consideredtransversely to the longitudinal axis of the light-emitting diodesurrounded thereby which increases when getting away from the supportface of the substrate according to the transverse direction and whichhas, over an upper portion of the height thereof located on the sideopposite to the support face of the substrate with respect to said lowerportion, a thickness considered transversely to the longitudinal axis ofthe light-emitting diode surrounded thereby which decreases at the levelof the upper border of the light-emitting diode when getting away fromthe support face of the substrate according to the transverse directionand wherein the formed light confinement walls have an inner face havinga concave shape matching with said convex shape and directed towards thelight-emitting diode for which it confines the light radiation thereof.

Some preferred, yet non-limiting, aspects of this manufacturing methodare as follows.

The step of forming the spacing walls comprises a step of depositing athin layer of the first material, implemented so that the deposited thinlayer covers the lateral sidewalls and the upper border of thelight-emitting diodes.

The second material used in the step of forming the light confinementwalls is such that the light confinement walls are reflective for thelight radiation originating from the light-emitting diodes.

The step of forming light confinement walls comprises a step ofdepositing a thin layer of the second material implemented so that thisthin layer of the second material directly covers the lateral sidewallsof the spacing walls by being in contact with the latter and covers theupper border of the light-emitting diodes and in that the step ofdepositing the thin layer of the second material comprises a step offilling, by said thin layer of the second material, the empty spacesdelimited between the spacing walls at the level of the areas betweenthe light-emitting diodes.

At the end of the step of forming the light confinement walls, the upperborder of each light-emitting diode is not covered by the secondmaterial so that the light radiation originating from the light-emittingdiodes is emitted out of the optoelectronic device by an emissionsurface of the optoelectronic device located, with respect to thelight-emitting diodes, on the side of the upper borders of thelight-emitting diodes according to the transverse direction.

At the end of the step of forming the light confinement walls, the upperborder of each light-emitting diode is covered by a light confinementwall so that after the implementation of a step of removing thesubstrate, the light radiation originating from the light-emittingdiodes is emitted out of the optoelectronic device by an emissionsurface of the optoelectronic device located, with respect to thelight-emitting diodes, on the side opposite to the upper borders of thelight-emitting diodes according to the transverse direction.

The first material used for the formation of the spacing walls includesphoto-luminescent particles which are in the form of quantum dots.

The invention also relates to an optoelectronic device comprising:

-   -   an array of light-emitting diodes where each light-emitting        diode has an elongate wire-like shape according to a        longitudinal axis extending according to a transverse direction        of the optoelectronic device,    -   spacing walls made of a first dielectric material transparent to        the light radiation originating from the light-emitting diodes        and arranged such that the lateral sidewalls of each        light-emitting diode, over the entire height thereof considered        according to the transverse direction, are surrounded by at        least one of the spacing walls,    -   and light confinement walls made of a second material adapted to        block the light radiation originating from the light-emitting        diodes, the light confinement walls directly covering the        lateral sidewalls of the spacing walls by being in contact with        the latter, the light radiation originating from each        light-emitting diode and directed in the direction of the        adjacent light-emitting diodes being blocked by the light        confinement wall which covers the spacing wall that surrounds        said light-emitting diode,

wherein the spacing walls have a convex-shaped outer face, at least oneof said spacing walls having, over a lower portion of the height thereofconsidered according to the transverse direction located on the side ofthe support face of the substrate, a thickness considered transverselyto the longitudinal axis of the light-emitting diode surrounded therebywhich increases when getting away from the support face of the substrateaccording to the transverse direction and having, over an upper portionof the height thereof located on the side opposite to the support faceof the substrate with respect to said lower portion, a thicknessconsidered transversely to the longitudinal axis of the light-emittingdiode surrounded thereby which decreases at the level of the upperborder of the light-emitting diode when getting away from the supportface of the substrate according to the transverse direction and whereinthe light confinement walls have an inner face having a concave shapematching with said convex shape and directed towards the light-emittingdiode for which it confines the light radiation thereof.

Some preferred, yet non-limiting, aspects of this optoelectronic deviceare as follows.

The light confinement walls cover the upper border of the light-emittingdiodes and the light radiation originating from the light-emittingdiodes is emitted out of the optoelectronic device by an emissionsurface of the optoelectronic device located, with respect to thelight-emitting diodes, on the side opposite to the upper borders of thelight-emitting diodes according to the transverse direction.

The second material is such that the light confinement walls arereflective for the light radiation originating from the light-emittingdiodes.

The optoelectronic device comprises a lower electrode layer made of anelectrically-conductive material transparent to the light radiation,said lower electrode layer being in electrical contact with the lowerborders of the light-emitting diodes in order to fill a function of afirst electrode common to several light-emitting diodes.

Each light-emitting diode is of the core-shell type and theoptoelectronic device comprises an upper electrode layer made of anelectrically-conductive material transparent to the light radiation, theupper electrode layer directly covering the lateral sidewalls and theupper border of the light-emitting diodes by being in contact with thelatter so as to fill a function of a second electrode common to severallight-emitting diodes, the spacing walls directly covering the lateralsidewalls and the upper border of the upper electrode layer by being incontact with the latter and the upper electrode layer being inelectrical contact with at least one of the light confinement walls.

The light confinement walls do not cover the upper border of thelight-emitting diodes and the light radiation originating from thelight-emitting diodes is emitted out of the optoelectronic device by anemission surface of the optoelectronic device located, with respect tothe light-emitting diodes, on the side of the upper borders of thelight-emitting diodes according to the transverse direction.

BRIEF DESCRIPTION OF THE DRAWINGS

Other aspects, objects, advantages and features of the invention willappear better on reading the following detailed description of preferredembodiments thereof, provided as a non-limiting example, and made withreference to the appended drawings in which:

FIGS. 1 and 2 illustrate two steps of an example of implementation of amanufacturing method according to the invention.

FIG. 3 illustrates a variant of FIG. 2.

FIG. 4 represents, in longitudinal section, another example of anoptoelectronic device that could be obtained through the implementationof a manufacturing method according to the invention.

FIGS. 5 and 6 represent, in longitudinal section, two other examples ofoptoelectronic devices that could be obtained through the implementationof a manufacturing method according to the invention.

FIGS. 7 and 8 represent, in top view, two examples of optoelectronicdevices manufactured through the implementation of a manufacturingmethod according to the invention.

DETAILED DISCLOSURE OF PARTICULAR EMBODIMENTS

In the figures and in the following description, the same referencenumerals represent identical or similar elements. In addition, thedifferent elements are not represented to scale so as to enhance clarityof the figures. Moreover, the different embodiments and variants do notexclude one another and may be combined together.

First, the invention relates to a manufacturing method for manufacturingan optoelectronic device 10 including an array of light-emitting diodes11. It also relates to an optoelectronic device 10 as such, includingthe array of light-emitting diodes 11.

Thanks to the arrangement of such an array of light-emitting diodes 11,a particularly targeted application is the supply of an images displayscreen or of an images projection device.

To this end, the array of light-emitting diodes 11 may have a determinedemission surface throughout which is transmitted the light radiationoriginating from the light-emitting diodes 11. In practice, the array oflight-emitting diodes 11 defines an array of light pixels where eachpixel includes one or several light-emitting diode(s) 11. In particular,each pixel may comprise:

-   -   at least one sub-pixel formed by at least one light-emitting        diode 11 adapted to directly generate, or to transmit via a        suitable light converter, blue light,    -   at least one sub-pixel formed by at least one light-emitting        diode 11 adapted to directly generate, or to transmit via a        suitable light converter, green light,    -   at least one sub-pixel formed by at least one light-emitting        diode 11 adapted to directly generate, or to transmit via a        suitable light converter, red light.

The manufacturing method comprises a step of forming the array oflight-emitting diodes 11 on a support face 12 of a substrate 13.

To facilitate understanding, a three-dimensional direct reference frame(X, Y, Z) is defined herein and for the following description, where theplane (X, Y) corresponds to the main plane of the optoelectronic device10 over which the light-emitting diodes 11 are distributed and where Zcorresponds to the transverse direction of the optoelectronic device 10directed transversely to the plane (X, Y). In other words, thedirections X and Y are generally directed parallel to the general planeof the support face 12 of the substrate 11 used in the manufacture ofthe optoelectronic device 10 and the transverse direction Z is directedtransversely to the support face 12 of the substrate 13.

During this step, each formed light-emitting diode 11 advantageously hasan elongate wire-like shape according to a longitudinal axis extendingaccording to the transverse direction Z of the optoelectronic device 10.

The layout of each light-emitting diode 11 in the form of a wire isquite advantageous for high-resolution and high-contrast optoelectronicdevices 10 while imposing no limitation with regards to the materialsand to the techniques used in the following steps of the manufacturingmethod and conferring all known advantages with regards to resort tosuch wire-like shaped light-emitting diodes 11, in particular in termsof the cost and effectiveness.

The techniques implemented to form the wire-like shaped light-emittingdiodes 11 are not restrictive with regards to the manufacturing methoddescribed in this document so that in order to implement this step offorming the light-emitting diodes 11, those skilled in the art couldresort to any known techniques.

In a way that is not illustrated in detail, each light-emitting diode 11comprises semiconductor elements including a first doped portion, anactive portion and a second doped portion. The semiconductor elementsare arranged in a wire-like shape, according to micrometric ornanometric dimensions.

Each light-emitting diode 11 in the form of a wire may indifferently beof the core-shell type or alternatively have an axial structure wherethe first doped portion, the active portion and the second doped portionare stacked according to the transverse direction Z. All knowntechniques for these purposes may be used, in particular by exploitingepitaxial growth principles.

The cross-section of the wire-like shaped light-emitting diodes 11,considered in any plane parallel to the plane (X, Y), may have differentshapes such as, for example, an oval, circular or polygonal (for examplesquare, rectangular, triangular or hexagonal) shape.

For example, in the case of a core-shell type layout, eachlight-emitting diode 11 comprises a wire forming the first dopedportion, whether this is of the N type or P type, extending transverselyto the plane of the support face 12 of the substrate 13, and a shellcovering at least the upper portion of this wire. The shell may comprisea stacking of several layers of semiconductor materials, in particularat least one layer forming the active portion covering at least theupper portion of the wire and a layer forming the second doped portionand covering the layer forming the active portion.

As example, the constitutive wires of the first doped portion may be, atleast partially, formed from semiconductor materials including mostly aIII-V compound, for example III-N compounds. Examples from the group IIIcomprise gallium, indium or aluminum. Examples of III-N compounds areGaN, AlN, InGaN or AlInGaN. Other elements from the group V may also beused, for example, phosphorus, arsenic or antimony. In general, theelements in the III-V compound may be combined with different molarfractions. It should be set out that the wires may indifferently beformed from semiconductor materials including mostly a II-VI compound.The dopant may be selected, in the case of a III-V compound, from thegroup comprising a P-type dopant from the group II, for examplemagnesium, zinc, cadmium or mercury, a P-type dopant from the group IVfor example carbon, or an N-type dopant from the group IV, for examplesilicon, germanium or selenium.

The active layer is the layer from which most of the radiation suppliedby the light-emitting diode 11 is emitted. It may include means forconfining the electric-charge carriers, such as quantum wells. Forexample, it is constituted by an alternation of GaN and InGaN layers.The GaN layers may be doped. Alternatively, the active layer may beconstituted by one single InGaN layer.

The layer forming the second doped portion, P-type doped if the wiresare N-type doped or N-type doped if the wires are P-type doped, maycorrespond to a semiconductor layer or a stacking of semiconductorlayers enabling the formation of a P-N or P-I-N junction.

In general, the first doped portion of the light-emitting diodes 11 isin electrical contact with a first lower electrode and the second dopedportion of the light-emitting didoes 11 is in electrical contact with asecond upper electrode. These considerations will be reviewed in-depthlater on only as example.

The manner for forming the first lower electrode and the second upperelectrode is not restrictive and all known techniques suited for theimplementation of the subsequent steps that will be described in thefollowing description, may, on the contrary, be considered by thoseskilled in the art. For example, the first lower electrode may be formedby the substrate 13 itself or by a conductive layer formed on thesupport face 12 of the substrate 13. The first lower electrode may alsobe formed after the removal of the substrate 13.

Hence, it shall be emphasized that the terms «formation of the array oflight-emitting diodes 11 on the support face 12» means either that thelight-emitting diodes 11 are directly formed on the support face 12 bymeans of a mechanical and electrical contact, or the light-emittingdiodes 11 are indirectly formed on the support face 12 by theinterposition of at least the conductive layer intended to ensure thefunction of a first lower electrode.

Hence, the substrate 13 may be at least partially formed in a conductiveor highly-doped semiconductor material so as to have good electricconductivity properties, for example constituted by silicon, preferablymonocrystalline.

The substrate 13 may also be formed by sapphire and even by a III-Vsemiconductor material, for example GaN.

Alternatively, it may consist of a «Silicon On Insulator» or «SOI» typesubstrate.

Alternatively, the substrate 13 may be formed in a semiconductor orelectrically-insulating material.

It arises from the foregoing that the first lower electrode may beformed by the substrate 13 itself or by a lower electrode layer 21,formed on the substrate 13 in an electrically-conductive material and inelectrical contact with the lower borders of the light-emitting diodes11 in order to fill a function of a first electrode common to severallight-emitting diodes 11.

In the case where an emission of light will be desired at the rear faceof the optoelectronic device 10, as is the case for example in theembodiments of FIGS. 5 and 6, the lower electrode layer 21 may betransparent to the light radiation 16 originating from thelight-emitting diodes 11 (it is set out that in this embodiment, thesubstrate 13 on which the light-emitting diodes 11 are formed is removedand the lower electrode layer 21 is formed after the removal of thesubstrate 13). But it is specified that this condition of transparencyof the layer 21 to the light radiation 16 is not mandatory, inparticular in the case where it would be desired that the emission oflight is achieved on the side of the front face of the optoelectronicdevice 10.

It is possible to provide for a layer of an electrically-insulatingmaterial between the substrate 13 and the lower electrode layer 21, forexample depending on the nature of the substrate 13, such anelectrically-insulating material layer remaining, nonetheless, optional.

The lower electrode layer 21 may comprise a nucleation layer or astacking of nucleation layers made of a material suited to the growth,on said material, of the semiconductor elements of the light-emittingdiodes 11.

As example, the material composing a nucleation layer may consist of anitride, a carbide or a boride of a transition metal from the column IV,V or VI of the periodic table of elements or a combination of thesecompounds. As example, the nucleation layer may be made of aluminumnitride, aluminum oxide, boron, boron nitride, titanium, titaniumnitride, tantalum, tantalum nitride, hafnium, hafnium nitride, niobium,niobium nitride, zirconium, zirconium boride, zirconium nitride, siliconcarbide, tantalum nitride and carbide, or magnesium nitride in the formMg_(x)N_(y), where x is equal to about 3 and y is equal to about 2, forexample magnesium nitride in the form Mg₃N₂. The nucleation layer may bedoped with the same conductivity type as that of the semiconductorelements intended to grow, and have a thickness comprised, for example,between 1 nm and 200 nm, preferably comprised between 10 nm and 50 nm.The nucleation layer may be composed of an alloy or of a stacking of oneor several material(s) mentioned in the list hereinabove.

The lower electrode layer 21 may comprise, besides the nucleationlayer(s) or instead of the nucleation layer(s), a conductive layer or astacking of conductive layers, in particular metallic.

In the case where an emission of light is desired on the side of thefront face of the optoelectronic device 10, the conductive layer(s) maycover the nucleation layer(s) between the light-emitting diodes 11 butwithout extending over the light-emitting diodes 11. For example, theconductive material used for such conductive layers is: aluminum,copper, gold, ruthenium, silver, zinc, titanium, nickel. In particular,properties enabling it to serve as a reflector to send back outwards thelight radiations 16 initially emitted by the light-emitting diodes 11 inthe direction of the substrate 13, may be desired.

In the case where an emission of light is desired on the side of therear face of the optoelectronic device 10, the conductive material usedfor such conductive layers may have transparency characteristics to thelight emitted by the light-emitting diodes 11. For example, the usedmaterial may be selected from any transparent conductive oxides, alsoknown under the acronym «TCO». In particular, it may be provided forforming the conductive layer(s), for example by deposition, after a stepof removing the substrate 13 and removing the nucleation layer(s).

Afterwards, the manufacturing method comprises a step of forming spacingwalls 14 made of a first material that is both dielectric andtransparent to the light radiation 16 (this light radiation beingschematized by arrows undergoing a reflection in FIGS. 4 to 6)originating from the light-emitting diodes 11. The spacing walls 14 areformed so that the lateral sidewalls 111 of each light-emitting diode11, over the entire height H thereof considered according to thetransverse direction Z, are surrounded by at least one of the spacingwalls 14. As example, the height H of the light-emitting diodes 11 iscomprised between 0.1 and 100 μm, preferably between 0.5 and 20 μm.

Hence, the first material used for the formation of the spacing walls 14has properties of transparency to the wavelengths intended for the lightradiations 16 originating from the active portions of the light-emittingdiodes 11 and, at the same time, electrical insulation properties. Forexample, it may consist of an oxide, a nitride and even, for example, asilicon oxynitride. Other materials may also be suitable, such as forexample organic materials, some resins or silicones, TiO₂ or HfO₂.

The first material used for the formation of the spacing walls 14 mayinclude photo-luminescent particles, adapted to convert the lightradiation 16 emitted by the light-emitting diodes 11 in terms ofwavelengths, in order to ultimately modify the color of the lightemitted out of the optoelectronic device 10. This solution may be usedto obtain pixels or sub-pixels of different colors without resorting toother additional color converters.

Preferably, the photo-luminescent particles are in the form of quantumdots, that is to say in the form of semiconductor nanocrystals whosequantum confinement is substantially three-dimensional. The average sizeof the quantum dots may then be comprised between 0.2 nm and 50 nm, forexample between 1 nm and 30 nm. The quantum dots may be made of at leastone semiconductor compound, which may be selected from cadmium selenide(CdSe), indium phosphide (InP), gallium and indium phosphide (InGaP),cadmium sulphide (CdS), zinc sulphide (ZnS), cadmium (CdO) or zinc (ZnO)oxide, zinc and cadmium selenide (CdZnSe), zinc selenide (ZnSe) dopedfor example with copper or manganese, graphene or from other possiblysuitable semiconductor materials. The size and the composition of thephoto-luminescent particles are selected according to the desiredluminescence wavelength. It may also consist of core-shell typestructures.

As shown in the different variants schematized in FIGS. 1 to 6, the stepof forming the spacing walls 14 is implemented so that the formedspacing walls 14 have a convex-shaped outer face and so that at leastone of said spacing walls 14 has, over a lower portion (denoted «PI») ofthe height thereof considered according to the transverse direction Zlocated on the side of the support face 12 of the substrate 13, athickness considered transversely to the longitudinal axis of thelight-emitting diode 11 surrounded thereby which increases when gettingaway from the support face 12 of the substrate 13 according to thetransverse direction Z and which has, over an upper portion (denoted«PS») of the height thereof located on the side opposite to the supportface 12 of the substrate 13 with respect to said lower portion PI, athickness considered transversely to the longitudinal axis of thelight-emitting diode 11 surrounded thereby which decreases at the levelof the upper border 112 of the light-emitting diode 11 when getting awayfrom the support face 12 of the substrate 13 according to the transversedirection Z. The formed light confinement walls 17 have an inner face172 having a concave shape matching with said convex shape and directedtowards the light-emitting diode 11 for which it confines the lightradiation 16 thereof.

On completion of their formation step, the spacing walls 14 are arrangedso as not to cover the upper borders 112 of the light-emitting diodes11.

According to a non-limiting particular mode of implementation of themanufacturing method, the step of forming the spacing walls 14 comprisesa step of depositing a thin layer 15 of the first material, implementedso that the deposited thin layer 15 covers the lateral sidewalls and theupper border 112 of the light-emitting diodes 11. The thin layer 15 maydirectly cover the lateral sidewalls and the upper borders 112 of thelight-emitting diodes 11 by being in contact with the latter.Alternatively, the thin layer 15 may cover them indirectly through theinterposition of at least one intermediate layer such as for example atleast one thin layer of a conductive material transparent to the lightradiations 16 intended to serve as a second upper electrode. Forexample, these arrangements are represented in FIG. 5 with the presenceof the layer bearing the reference numeral 22 which will be described inmore detail in the following description.

The thin layer 15 may be deposited by chemical vapor deposition, forexample by atomic layer deposition, and even by physical vapordeposition, for example by electron beam, by cathode sputtering, or thesame.

In general, the thin layer 15 has an average thickness (this averagethickness being substantially homogeneous in the particular embodimentproviding for a conformal deposition of the material) which may becomprised between 100 nm and 10 μm, and preferably between 500 nm and 5μm, for example comprised between 1 μm and 2 μm, at the level of thelateral sidewalls of the light-emitting diodes 11.

In particular, the thickness of the thin layer 15 may result from atradeoff between its function of self-aligning the light confinementwalls 17 described later on, and the output of the best possibleresolution.

Thus, the thin layer 15 may continuously cover the lateral sidewalls ofthe light-emitting diodes 11, their upper borders 112 and the areasbetween the light-emitting diodes 11.

In the second example of implementation of the manufacturing methodrepresented in the figures, the deposition of the thin layer 15 isperformed in a non-conformal way, meaning that the thickness of the thinlayer 15 has large variations after deposition. In particular, thethickness of the thin layer 15 decreases progressively as it approachesthe link area between the light-emitting diodes 11 and the substrate 13,that is to say at the level of their lower borders. This progressivedecrease is performed along the lateral sidewalls of the light-emittingdiodes 11 as well as along the areas separating the light-emittingdiodes 11 from one another.

The spacing walls 14 may cover, whether directly or indirectly, theupper borders 112 of the light-emitting diodes 11, as is for example thecase in FIGS. 1 to 4. The spacing walls 14 will essentially correspondto the formed thin layer 15.

The manufacturing method comprises a step of forming light confinementwalls 17 made of a second material adapted to block the light radiation16 originating from the light-emitting diodes 11. By «block the lightradiation», it should be understood that either the material absorbs theincident light radiation so that it does not cross this material, or thematerial has properties of reflection of the incident light radiation onthis material.

The formed light confinement walls 17 directly cover the lateralsidewalls 141 of the spacing walls 14 by being in contact with thelatter, so that the light radiation 16 originating from eachlight-emitting diode 11 and directed in the direction of the adjacentlight-emitting diodes 11 is blocked (by absorption or reflection) by thelight confinement wall 17 which covers the spacing wall 14 thatsurrounds this light-emitting diode 11.

By «light radiation 16 originating from the light-emitting diodes 11»,it should be understood that it either consists of the light radiationsdirectly emitted by the light-emitting diodes 16, or it consists of thelight radiations converted by possible color converters, for examplethrough photo-luminescent particles in the first material used for theformation of the spacing walls 14.

The presence of such light confinement walls 17 allows avoiding thelight radiations 16 originating from the light-emitting diodes 11 beingmixed from one light-emitting diode 11 to another in order to be able toensure a high contrast.

In other words, while it possible to provide for the second materialused in the step of forming the light confinement walls 17 to be opaqueonly to the light radiations 16 originating from the light-emittingdiodes 11, it is quite advantageous to guarantee that this secondmaterial is such that the light confinement walls 17 are reflective tothe light radiations 16 originating from the light-emitting diodes 11.This allows increasing the efficiency of the set and possibly achievingan emission of the light radiations 16 out of the optoelectronic device10 on the side of the rear face after removal of the substrate 13.

The second material having such reflective properties with regards tothe light radiations 16 may be made of the same reflective material orof a plurality of different materials deposited on top of one another.The reflective materials may be selected from aluminum, silver, nickel,platinum, or any other suitable material.

In general, any technique may be considered by those skilled in the artto form such light confinement walls 17.

According to a non-limiting particular mode of implementation of themanufacturing method, with reference to FIG. 1, the step of forming thelight confinement walls 17 comprises a step of depositing a thin layer19 of the second material implemented so that this thin layer 19 of thesecond material covers not only the lateral sidewalls 141 of the spacingwalls 14 by being in direct contact with the latter but also the upperborders 112 of each of the light-emitting diodes 11 by being in contact,or not (for example in the case where the upper borders 112 are alreadycovered by the layer forming the second upper electrode and/or by aportion of the spacing walls 14), with it.

As illustrated in FIG. 1, the step of depositing the thin layer 19 ofthe second material may, for example, comprise a step of filling, bythis thin layer 19 of the second material, the empty spaces delimitedbetween the spacing walls 14 at the level of the areas between thelight-emitting diodes 11.

Nonetheless, the deposition of the thin layer 19 may be carried out byany technique known to those skilled in the art, the choice may dependfor example on the nature of the deposited material, its thickness or onthe voids externally separating the spacing walls 14. The thickness ofthe deposited thin layer 19 may be sufficiently larger than the height Hof the light-emitting diodes 11 so as to ensure, where necessary, thesecond material being able to cover the upper borders 112 of thelight-emitting diodes 11, in the case where a reflection of the lightradiations 16 is desired at this location. Yet, as shown in FIG. 5, itis possible to ensure that the thin layer intended to form the lightconfinement walls 17 covers the upper borders 112 of the diodes 11despite a thickness of this thin layer being substantially smaller thanH.

The example of implementation of the manufacturing method illustrated inFIGS. 1 and 1 also provides for the deposition of the thin layer 19(FIG. 1) between and over the spacing walls 14 formed beforehand througha deposition promoting an irregular thickness as already explained. Atthe contact with the spacing walls 14, the thin layer 19 has a shapematching with the spacing walls 14 by conforming to their externalshapes. The result is that the same will apply to the light confinementwalls 17 obtained subsequently to the deposition of the thin layer 19.The thin layer 19 then covers the lateral sidewalls and the upperborders of the spacing walls 14 which, in turn, cover the upper borders112 and the lateral sidewalls of the light-emitting diodes 11.

In the case where the extraction of the emitted light is desired by thefront face of the optoelectronic device 10, that is to say on the sideopposite to the substrate 13 having been used for the manufacture, themanufacturing method will be carried out so that on completion of thestep of forming the light confinement walls 17, the upper border 112 ofeach light-emitting diode 11 is not covered by the second material sothat the light radiation 16 originating from the light-emitting diodes11 is emitted out of the optoelectronic device 10 by an emission surfaceof the optoelectronic device 10 located, with respect to thelight-emitting diodes 11, on the side of the upper borders 112 of thelight-emitting diodes 11 according to the transverse direction Z.

Thus, after the step of depositing the thin layer 19 of the secondmaterial, in order to end up with the configuration of FIGS. 2 to 4, thestep of forming the light confinement walls 17 may comprise an optionalstep of etching and/or a step of chemical-mechanical polishing the thinlayer 19 of the second material deposited beforehand, on the sideopposite to the substrate 13 according to the transverse direction Z.This etching and/or chemical-mechanical polishing step may beimplemented by any technique known to those skilled in the art. Inparticular, when desired, an object of this step is to ensure that thelight confinement walls 17 do not cover the upper borders 112 of thelight-emitting diodes 11, in particular in order to allow emitting thelight radiations 16 out of the optoelectronic device 10 by the frontface.

While FIG. 2 illustrates an example wherein a planarization of thepreviously-deposited thin layer 19 is carried out by etching orchemical-mechanical polishing until removing all of the second materialon top of the upper borders 112 of the light-emitting diodes 11, theseupper borders 112 being still covered by the first materialcorresponding to the spacing wall 14 (the light confinement walls 17only covering the lateral sidewalls of the spacing walls 14), FIG. 3schematizes the variant of FIG. 2 which corresponds to the particularcase where the step of etching the thin layer 19 is a selective etching,meaning that the second material is etched and the first materialremains substantially intact (in other words, the shape of the spacingwalls 14 is identical at the level of the upper borders 112 of thelight-emitting diodes 11 whether before or after said step of etchingthe thin layer 19).

In the manufacturing method that has just been described, the spacingwalls 14 over which the light confinement walls 17 are directly formedensure, quite advantageously, a function of self-aligning the formedlight confinement walls 17. Since the spacing walls 14 are, in turn,formed aligned with respect to the light-emitting diodes 11 surroundedthereby, this results in an advantageous phenomenon of self-alignment ofthe light confinement walls 17 with respect to the light-emitting diodes11. This allows obtaining quite accurately aligned light confinementwalls 17 even in the case of light-emitting diodes 11 that are spacedapart according to a very small step in the plane (X, Y). The result isthe possibility of providing an optoelectronic device 10 having both ahigh contrast (thanks to the presence of the light confinement walls 17)and a high resolution, in a simple and economical manner.

By providing for the step of forming the light confinement walls 17 tocomprise the deposition of the thin layer 19 as previously described,that is to say in particular where the thin layer 19 directly covers thelateral sidewalls 141 of the spacing walls 14 by being in contact withthe latter and covers the upper border 112 of the light-emitting diodes11, it is possible to provide a solution that is simple, non-restrictiveand economical to implement yet without altering in any mannerwhatsoever the obtained contrast and resolution levels.

The particular shapes of the previously-described spacing walls 14, thatis to say featuring a progressive increase in thickness along the lowerportion PI and a progressive decrease along the upper portion PS asdescribed hereinbefore, are advantageous for the emitted light toundergo a collimation within a reduced cone, such as for example a lightbeam opening characterized by a value NA (standing for «NumericalAperture») in the range of 0.3. The effect of such concave shapes of thereflective inner faces 172 is even more effective for a wire-like shapedlight-emitting diode 11 in order to ensure the collimation of theemitted light so as to be partially emitted parallel to the axis of thewire-like shaped first doped portions of the light-emitting diodes 11,while such light-emitting diodes 11 intrinsically have a heart-likeshaped far field.

FIGS. 7 and 8 represent, in partial top view, two examples ofoptoelectronic devices 10 manufactured through the implementation of thepreviously-described manufacturing method. While FIG. 7 shows that theformed light confinement walls 17 may be such that the light-emittingdiodes 11 are separate and made individual, FIG. 8 illustrates the factthat the monitoring of the thickness of the spacing walls 14 formed atthe level of the lateral sidewalls 112 of the light-emitting diodes 11and the monitoring of the step between the light-emitting diodes 11allow making light confinement walls 17 for sub-pixels with severallight-emitting diodes 11. In particular, by locally adapting the stepbetween the light-emitting diodes 11 appropriately, it is possible toobtain a coalescence of the spacing walls 14 for some light-emittingdiodes 11, as shown in FIG. 8 in contrast with FIG. 7.

Optionally, after the step of forming the light-emitting walls 17, themethod comprises a step of removing the first material that has beenused in the temporary constitution of the spacing walls 14. While thecreated voids could possibly be left empty once this removal iscompleted, it may be considered to provide for an additional stepconsisting in filling the voids created by the removal of the firstmaterial with a third filler material. For example, the third fillermaterial may be constituted by a silicone material or by a materialadapted to ensure a light converter function. Any material that issuited to this function may be considered by those skilled in the art.

When the extraction of the emitted light is desired to occur by the rearface of the optoelectronic device 10, that is to say on the side of thebase of the light-emitting diodes 11 opposite to their upper borders112, the manufacturing method is carried out so that at the end of thestep of forming the light confinement walls 17, the upper border 112 ofeach light-emitting diode 11 is also covered (directly as is the case inFIG. 6; or indirectly as is the case in FIG. 5) by a light confinementwall 17 so that after the implementation of a step of removing thesubstrate 13, the light radiation 16 originating from the light-emittingdiodes 11 is emitted out of the optoelectronic device 10 by an emissionsurface 20 of the optoelectronic device 10 located, with respect to thelight-emitting diodes 11, on the side opposite to the upper borders 112of the light-emitting diodes 11 according to the transverse direction Z.These are for example the configurations of FIGS. 5 and 6.

In each of FIGS. 5 and 6, in which one single pixel is represented formerely illustrative purposes, the optoelectronic device 10 thereforecomprises:

-   -   an array of light-emitting diodes 11 where each light-emitting        diode 11 features the previously-described wire-like shape, that        is to say elongate according to a longitudinal axis extending        according to the transverse direction Z of the optoelectronic        device 10,    -   the spacing walls 14 made of the first material as previously        described, arranged such that the lateral sidewalls of each        light-emitting diode 11, over the entire height H thereof, are        surrounded by at least one of these spacing walls 14,    -   and the light confinement walls 17 made of the second material        as previously described, and directly covering the lateral        sidewalls 141 of the spacing walls 14 by being in contact with        the latter and covering the upper border 112 of the        light-emitting diodes 11.

In each of the examples of FIGS. 5 and 6, the spacing walls 14 have aconvex-shaped outer face, at least one of said spacing walls 14 having,over a lower portion PI of the height thereof considered according tothe transverse direction Z located on the side of the support face 12 ofthe substrate 13, a thickness considered transversely to thelongitudinal axis of the light-emitting diode 11 surrounded therebywhich increases when getting away from the support face 12 of thesubstrate 13 according to the transverse direction Z and having, over anupper portion PS of the height thereof located on the side opposite tothe support face 12 of the substrate 13 with respect to said lowerportion PI, a thickness considered transversely to the longitudinal axisof the light-emitting diode 11 surrounded thereby which decreases at thelevel of the upper border 112 of the light-emitting diode 11 whengetting away from the support face 12 of the substrate 13 according tothe transverse direction Z and the light confinement walls 17 have aninner face 172 having a concave shape matching with said convex shapeand directed towards the light-emitting diode 11 for which it confinesthe light radiation 16 thereof. The entirety of the convex surfacedelimited by the spacing walls 14 is covered by the light confinementwalls 17.

The light confinement walls 17 that cover the lateral sidewalls of thelight-emitting diodes 11 enable the light radiation 16 originating fromeach light-emitting diode 11 and directed in the direction of theadjacent light-emitting diodes 11 to be blocked by the light confinementwall 17 that covers the spacing wall 14 which surrounds thislight-emitting diode 11. At the same time, since the light confinementwalls 17 also cover the upper borders 112 of the light-emitting diodes11, the light radiation 16 originating from the light-emitting diodes 11is emitted out of the optoelectronic device 10 by an emission surface 20of the optoelectronic device 10 located, with respect to thelight-emitting diodes 11, on the side opposite to the upper borders 112of the light-emitting diodes 11 according to the transverse direction Z.

In each of the examples of FIGS. 5 and 6, the aforementioned lowerelectrode layer 21, formed after removal of the substrate 13, istransparent to the light radiation 16 originating from thelight-emitting diodes 11. The lower electrode layer 21 is in electricalcontact with the lower borders of the light-emitting diodes 11 so thatthe first lower electrode is common to several light-emitting diodes 11.Thus, subsequently to the formation of the light-emitting diodes 11, thespacing walls 14 and the confinement walls 17, the manufacturing methodcomprises a step of removing the substrate 13 then a step of forming thelower electrode layer 21, typically by deposition, over the face clearedafter the removal of the substrate 13. For example, the material usedfor the formation of the lower electrode layer 21 may be selected fromany transparent conductive oxides, also known under the acronym «TCO».

To obtain the optoelectronic device 10 of FIG. 5, at least oneinsulating layer 23 is formed on the upper face of the substrate 13before the formation of the light-emitting diodes 11, said at least oneinsulating layer 23 allowing avoiding an electrical contact between thelower electrode layer 21 and the upper electrode layer 22.

In FIG. 5, each light-emitting diode 11 is of the core-shell type. Theselight-emitting diodes 11 are obtained, for example, by epitaxial growthstarting from a continuous nucleation layer or from nucleation padsdistributed over the substrate 13, in the insulating layer 23. Theoptoelectronic device 10 also comprises the upper electrode layer 22made of an electrically-conductive material transparent to the lightradiation emitted by the light-emitting diodes 11. The upper electrodelayer 22, where the material used therein may be selected from anytransparent conductive oxides TCO known to those skilled in the art,directly covers the lateral sidewalls and the upper border 112 of thelight-emitting diodes 11 by being in contact with the latter so as toconstitute a second upper electrode common to several light-emittingdiodes 11. Afterwards, the spacing walls 14 directly cover the lateralsidewalls and the upper border of the upper electrode layer 22 by beingin contact with the latter. Then, the light confinement walls 17 areformed. The upper electrode layer 22 is in electrical contact with atleast one of the light confinement walls 17 which are formed on thespacing walls 14, in particular in the upper portion thereof. Thesubstrate 13 is removed and then the lower electrode layer 21 is formedon said at least one insulating layer 23 and so as to be in contact withthe lower borders of the light-emitting diodes. The indentation, bearingthe reference numeral 24, allows illustrating the etching undergone bythe second material by the front face thereof, to insulate the secondupper electrodes from one sub-pixel to another. The light confinementwalls 17 are externally embedded within a first insulating layer 25,over which the power supply and control device 26 is formed by means ofan electrical contact between this device 26 and the upper portions ofthe light confinement walls 17. In turn, the power supply and controldevice 26 is embedded within a second insulating layer 27. Any techniquefor forming the power supply and control device 26, the first insulatinglayer 25 and the second insulating layer 27 may be considered.

It shall be understood that in the optoelectronic device 10 of FIG. 5,the light confinement walls 17, thanks to their conductive properties,are part of the constitution of the second upper electrodecomplementarily with the upper electrode layers 22 which, in turn, aredirectly in contact with the second doped portions of the shell of thelight-emitting diodes 11. These participate in the electrical connectionwith the power supply and control device 26.

The optoelectronic device 10 of FIG. 6 is substantially identical tothat of FIG. 5 with the exception that each light-emitting diode 11 has,in this instance, an axial structure and that the upper electrode layer22 is absent because of the axial structure of the light-emitting diodes11. In this instance, the electrically-insulating layer 23 formed on thelower electrode layer 21 allows avoiding an electrical contact betweenthe lower electrode layer 21 and the light confinement walls 17 which,alone, fill the function of a second upper electrode. It is actually thesecond doped portions of the light-emitting diodes 11 that are in directcontact with the light confinement walls 17, at the level of the upperborders 112 of the light-emitting diodes 11.

As example, the convex shapes delimited by the spacing walls 14 may beparabolic, so that the light confinement walls 17 then have acomplementary concave parabolic shape, as is the case in each of FIGS. 5and 6. It is then quite advantageous, in the case of light-emittingdiodes 11 having an axial structure, to ensure, through an adaptedmonitoring of the conditions of formation of the spacing walls 14, thatthis concave parabola is shaped such that the active portion of thelight-emitting diode 11 adapted to emit the light radiation 16 islocated at the focus of the concave parabola.

Nonetheless, the spacing walls 14 may have convex shapes other thanparabolic.

In the example of optoelectronic device 10 of FIG. 4, unlike thearrangements of FIGS. 5 and 6, the light confinement walls 17 do notcover the upper border 112 of the light-emitting diodes 11 so that thelight radiation 16 originating from the light-emitting diodes 11 isemitted out of the optoelectronic device 10 by an emission surface ofthe optoelectronic device 10 located, with respect to the light-emittingdiodes 11, on the side of the upper borders 112 of the light-emittingdiodes 11 according to the transverse direction Z.

In FIG. 4, in which only two light-emitting diodes 11 are representedfor merely illustrative purposes, the optoelectronic device 10 thereforecomprises:

-   -   an array of light-emitting diodes 11 where each light-emitting        diode 11 features the previously-described wire-like shape, that        is to say elongate according to a longitudinal axis extending        according to the transverse direction Z of the optoelectronic        device 10,    -   the spacing walls 14 made of the first material as previously        described, arranged such that the lateral sidewalls of each        light-emitting diode 11, over the entire height H thereof, are        surrounded by at least one of these spacing walls 14,    -   and the light confinement walls 17 made of the second material        as previously described, and directly covering the lateral        sidewalls 141 of the spacing walls 14 by being in contact with        the latter but without covering the upper border of the        light-emitting diodes 11.

In the example of FIG. 4, the spacing walls 14 have a convex-shapedouter face, at least one of said spacing walls 14 having, over a lowerportion PI of the height thereof considered according to the transversedirection Z located on the side of the support face 12 of the substrate13, a thickness considered transversely to the longitudinal axis of thelight-emitting diode 11 surrounded thereby which increases when gettingaway from the support face 12 of the substrate 13 according to thetransverse direction Z and having, over an upper portion PS of theheight thereof located on the side opposite to the support face 12 ofthe substrate 13 with respect to said lower portion PI, a thicknessconsidered transversely to the longitudinal axis of the light-emittingdiode 11 surrounded thereby which decreases at the level of the upperborder 112 of the light-emitting diode 11 when getting away from thesupport face 12 of the substrate 13 according to the transversedirection Z and the light confinement walls 17 have an inner face 172having a concave shape matching with said convex shape and directedtowards the light-emitting diode 11 for which it confines the lightradiation 16 thereof. Only part of the convex surface delimited by thespacing walls 14 is covered by the light confinement walls 17.

Still in the example of FIG. 4, the first lower electrode is constitutedby the substrate 13 itself. The lower borders of the light-emittingdiodes 11 are in contact with the substrate 13, for example throughoutthe nucleation layer or nucleation pads, to create the electricalcontact. The substrate 13 integrates across the thickness thereofelectrically-insulating elements 30 extending through the substrate 13and delimiting, in pairs, portions of the substrate 13 that areelectrically insulated from one another.

The electrically-insulating elements 30 may comprise trenches eachextending across the entire thickness of the substrate 13 and filledwith an electrically-insulating material, for example an oxide, inparticular silicon oxide, or an insulating polymer. Alternatively, asillustrated in FIG. 4, the walls of each trench are covered with aninsulating layer 31, the remainder of the trench being filled with asemiconductor or conductive material 32, for example polycrystallinesilicon. According to another variant, the electrically-insulatingelements 30 comprise regions doped with a polarity type opposite to thesubstrate 13. As example, each trench has a width larger than 1 micron.The electrically-insulating elements 30 may comprise a first series ofsuch trenches directed according to the lateral direction Y and thusstepped along the longitudinal direction X and a second series of suchtrenches directed according to the longitudinal direction X andtherefore stepped along the lateral direction Y. This allows reaching amatrix-like layout of the light-emitting diodes 11 in the plane of thesubstrate 13.

It should be set out herein that such electrically-insulating elements30 may quite possibly be implemented even in the case where thesubstrate 13 is made of a semiconductor or electrically-insulatingmaterial, for heat resistance reasons.

Electrical contacts 33 that are necessary for the pixelation of theoptoelectronic device 10 are formed on the rear face of theoptoelectronic device 10. More specifically, the electrical contacts 33are formed so as to be in electrical contact with the rear face of thesubstrate 13.

To obtain the optoelectronic device 10 of FIG. 4, at least oneinsulating layer 23 is formed on the upper face of the substrate 13before the formation of the light-emitting diodes 11, said at least oneinsulating layer 23 allowing avoiding an electrical contact between thesubstrate 13 and the upper electrode layer 22.

In FIG. 4, each light-emitting diode 11 is for example obtained byepitaxial growth starting from a continuous nucleation layer or fromnucleation pads distributed over the substrate 13, in openings of theinsulating layer 23. The optoelectronic device 10 also comprises theupper electrode layer 22 made of an electrically-conductive materialtransparent to the light radiation emitted by the light-emitting diodes11. The upper electrode layer 22, the material used therein may beselected from any transparent conductive oxides TCO known to thoseskilled in the art, directly covers the lateral sidewalls and the upperborder 112 of the light-emitting diodes 11 by being in contact with thelatter so as to constitute a second upper electrode common to severallight-emitting diodes 11. Afterwards, the spacing walls 14 directlycover the lateral sidewalls and the upper border of the upper electrodelayer 22 by being in contact with the latter. Then, the lightconfinement walls 17 are formed. The upper electrode layer 22 is inelectrical contact with at least one of the light confinement walls 17that are formed on the spacing walls 14, in the interface area bearingthe reference numeral 28 between the upper electrode layer 22 and thelight confinement walls 17. The confinement walls 17 are discontinuous,in particular in the form of indentations obtained by etching of thesecond material by the front face thereof, to insulate the second upperelectrodes from one sub-pixel to another. An electrically-insulatingmaterial 29 may be attached in these indentations.

In a variant of FIG. 4 that is not illustrated, where the first lowerelectrode is no longer constituted by the substrate 13 itself, thesubstrate 13 is removed and then a lower electrode layer is formed onsaid at least one insulating layer 23 previously formed on the substrate13, this lower electrode layer being in contact with the lower bordersof the light-emitting diodes 11. Then, electrical contacts that arenecessary for the pixelation of the optoelectronic device 10 are formedon the rear face of the optoelectronic device 10. More specifically, theelectrical contacts are then formed so as to be in electrical contactwith the rear face of the lower electrode layer.

The invention claimed is:
 1. A manufacturing method for manufacturing anoptoelectronic device including an array of light-emitting diodes,including the following steps: formation of the array of light-emittingdiodes on a support face of a substrate, this step being carried out sothat each light-emitting diode of the array of light-emitting diodes hasan upper border and an elongate wire-like shape according to alongitudinal axis extending according to a transverse direction of theoptoelectronic device directed transversely to the support face of thesubstrate, formation of spacing walls made of a first dielectricmaterial transparent to light radiation originating from eachlight-emitting diode of the array of light-emitting diodes such thatlateral sidewalls of each light-emitting diode of the array oflight-emitting diodes, over an entire height thereof consideredaccording to the transverse direction, are surrounded by at least one ofthe spacing walls, formation of light confinement walls made of a secondmaterial adapted to block the light radiation originating from eachlight-emitting diode of the array of light-emitting diodes that directlycover lateral sidewalls of the spacing walls by being in contact withthe lateral sidewalls of the spacing walls, so that the light radiationoriginating from each light-emitting diode of the array oflight-emitting diodes and directed in a direction of at least oneadjacent light-emitting diode of the array of light-emitting diodes isblocked by one of the light confinement walls that covers one of thespacing walls that surrounds a corresponding light-emitting diode of thearray of light-emitting diodes, wherein the step of formation of spacingwalls is implemented so that the spacing walls have an outer face with aconvex shape and so that at least one of the spacing walls has, over alower portion of a height thereof considered according to the transversedirection located on a side of the support face of the substrate, athickness considered transversely to a longitudinal axis of a respectivelight-emitting diode of the array of light-emitting diodes surrounded bythe at least one of the spacing walls which increases when getting awayfrom the support face of the substrate according to the transversedirection and which has, over an upper portion of a height thereoflocated on a side opposite to the support face of the substrate withrespect to the lower portion, a thickness considered transversely to thelongitudinal axis of the respective light-emitting diode of the array oflight-emitting diodes surrounded by the at least one of the spacingwalls which decreases at the upper border of the respectivelight-emitting diode of the array of light-emitting diodes when gettingaway from the support face of the substrate according to the transversedirection and each light confinement wall has an inner face having aconcave shape matching with the convex shape, and the inner face beingdirected towards one of the light-emitting diodes of the light-emittingdiodes to confine the light radiation.
 2. The manufacturing methodaccording to claim 1, wherein the step of forming the spacing wallscomprises a step of depositing a thin layer of the first dielectricmaterial, implemented so that the deposited thin layer covers thelateral sidewalls and the upper border of each light-emitting diode ofthe array of light-emitting diodes.
 3. The manufacturing methodaccording to claim 2, wherein the second material used in the step offorming the light confinement walls is such that the light confinementwalls are reflective for the light radiation originating from eachlight-emiiting diode of the array of light-emitting diodes.
 4. Themanufacturing method according to claim 3, wherein the step of formationof light confinement walls comprises a step of depositing a thin layerof the second material implemented so that the thin layer of the secondmaterial directly covers the lateral sidewalls of the spacing walls bybeing in contact with the spacing walls and covers the upper border ofeach light-emitting diode of the array of light-emitting diodes and thestep of depositing the thin layer of the second material comprises astep of filling, by the thin layer of the second material, empty spacesdelimited between the spacing walls at a level of areas between eachlight-emitting diode of the array of light-emitting diodes.
 5. Themanufacturing method according to claim 4, wherein at an end of the stepof formation of the light confinement walls, the upper border of eachlight-emitting diode of the array of light-emitting diodes is notcovered by the second material so that the light radiation originatingfrom each light-emitting diode of the array of light-emitting diodes isemitted out of the optoelectronic device by an emission surface of theoptoelectronic device located, with respect to each light-emitting diodeof the array of light-emitting diodes, on a side of the upper border ofeach light-emitting diode of the array of light-emitting diodesaccording to the transverse direction.
 6. The manufacturing methodaccording to claim 5, wherein the first dielectric material used forformation of the spacing walls includes photo-luminescent particleswhich are in the form of quantum dots.
 7. The manufacturing methodaccording to claim 4, wherein at an end of the step of formation of thelight confinement walls, the upper border of each light-emitting diodeof the array of light-emitting diodes is covered by a light confinementwall so that after implementation of a step of removing the substrate,the light radiation originating from each light-emitting diode of thearray of light-emitting diodes is emitted out of the optoelectronicdevice by an emission surface of the optoelectronic device located, withrespect to each light-emitting diode of the array of light-emittingdiodes, on a side opposite to the upper border of each light-emittingdiode of the array of light-emitting diodes according to the transversedirection.
 8. The manufacturing method according to claim 7, wherein thefirst dielectric material used for formation of the spacing wallsincludes photo-luminescent particles which are in the form of quantumdots.
 9. The manufacturing method according to claim 2, wherein the stepof formation of light confinement walls comprises a step of depositing athin layer of the second material implemented so that the thin layer ofthe second material directly covers the lateral sidewalls of the spacingwalls by being in contact with the spacing walls and covers the upperborder of each light-emitting diode of the array of light-emittingdiodes and the step of depositing the thin layer of the second materialcomprises a step of filling, by the thin layer of the second material,empty spaces delimited between the spacing walls at a level of areasbetween each light-emitting diode of the array of light-emitting diodes.10. The manufacturing method according to claim 1, wherein the secondmaterial used in the step of forming the light confinement walls is suchthat the light confinement walls are reflective for the light radiationoriginating from each light-emitting diode of the array oflight-emitting diodes.
 11. The manufacturing method according to claim1, wherein the step of formation of light confinement walls comprises astep of depositing a thin layer of the second material implemented sothat the thin layer of the second material directly covers the lateralsidewalls of the spacing walls by being in contact with the spacingwalls and covers the upper border of each light-emitting diode of thearray of light-emitting diodes and the step of depositing the thin layerof the second material comprises a step of filling, by the thin layer ofthe second material, empty spaces delimited between the spacing walls ata level of areas between the each light-emitting diode of the array oflight-emitting diodes.
 12. The manufacturing method according to claim1, wherein at an end of the step of formation of the light confinementwalls, the upper border of each light-emitting diode of the array oflight-emitting diodes is not covered by the second material so that thelight radiation originating from each light-emitting diode of the arrayof light-emitting diodes is emitted out of the optoelectronic device byan emission surface of the optoelectronic device located, with respectto each light-emitting diode of the array of light-emitting diodes, on aside of the upper border of each light-emitting diode of the array ofthe light-emitting diodes according to the transverse direction.
 13. Themanufacturing method according to claim 1, wherein at an end of the stepof formation of the light confinement walls, the upper border of eachlight-emitting diode of the array of light-emitting diodes is covered bya light confinement wall so that after implementation of a step ofremoving the substrate, the light radiation originating from eachlight-emitting diode of the array of light-emitting diodes is emittedout of the optoelectronic device by an emission surface of theoptoelectronic device located, with respect to each light-emitting diodeof the array of light-emitting diodes, on a side opposite to the upperborder of each light-emitting diode of the array of light-emittingdiodes according to the transverse direction.
 14. The manufacturingmethod according to claim 1, wherein the first dielectric material usedfor formation of the spacing walls includes photo-luminescent particleswhich are in the form of quantum dots.
 15. An optoelectronic devicecomprising: an array of light-emitting diodes where each light-emittingdiode of the array of light-emitting diodes has an elongate wire-likeshape according to a longitudinal axis extending according to atransverse direction of the optoelectronic device, spacing walls made ofa first dielectric material transparent to light radiation originatingfrom each light-emitting diode of the array of light-emitting diodes,the spacing wall being arranged such that lateral sidewalls of eachlight-emitting diode of the array of light-emitting diodes, over anentire height thereof considered according to the transverse direction,are surrounded by at least one of the spacing walls, light confinementwalls made of a second material adapted to block the light radiationoriginating from each light-emitting diode of the array oflight-emitting diodes, the light confinement walls directly coveringlateral sidewalls of the spacing walls by being in contact with thespacing walls, the light radiation originating from each light-emittingdiode of the array of light-emitting diodes and directed in thedirection of at least one adjacent light-emitting diode of the array oflight-emitting diodes being blocked by one of the light confinementwalls that covers one of the spacing walls that surrounds acorresponding light-emitting diode of the array of light-emittingdiodes, wherein the spacing walls have a convex-shaped outer face, atleast one of the spacing walls having, over a lower portion of a heightthereof considered according to the transverse direction located on aside of a support face of a substrate, a thickness consideredtransversely to a longitudinal axis of a respective light-emitting diodeof the array of light-emitting diodes surrounded thereby which increaseswhen getting away from the support face of the substrate according tothe transverse direction and having, over an upper portion of the heightthereof located on a side opposite to the support face of the substratewith respect to the lower portion, a thickness considered transverselyto the longitudinal axis of the respective light-emitting diode of thearray of light-emitting diodes surrounded thereby which decreases at alevel of an upper border of the respective light-emitting diode of thearray of light-emitting diodes when getting away from the support faceof the substrate according to the transverse direction and the lightconfinement walls have an inner face having a concave shape matchingwith the convex-shaped outer face and directed towards one of thelight-emitting diodes of the array of light-emitting diodes for which itconfines the light radiation thereof.
 16. The optoelectronic deviceaccording to claim 15, wherein the light confinement walls cover theupper border of each light-emitting diode of the array of light-emittingdiodes and the light radiation originating from each light-emittingdiode of the array of the light-emitting diodes is emitted out of theoptoelectronic device by an emission surface of the optoelectronicdevice located, with respect to each light-emitting diode of the arrayof light-emitting diodes, on a side opposite to the upper border of eachlight-emitting diode of the array of light-emitting diodes according tothe transverse direction.
 17. The optoelectronic device according toclaim 15, wherein the second material is such that the light confinementwalls are reflective for the light radiation originating from eachlight-emitting diode of the array of light-emitting diodes.
 18. Theoptoelectronic device according to claim 15, wherein the optoelectronicdevices comprises a lower electrode layer made of anelectrically-conductive material transparent to the light radiation, thelower electrode layer being in electrical contact with lower borders ofeach light-emitting diode of the array of light-emitting diodes in orderto fill a function of a first electrode common to several light-emittingdiodes of the array of light-emitting diodes.
 19. The optoelectronicdevice according to claim 15, wherein each light-emitting diode of thearray of light-emitting diodes is of a core-shell type and eachlight-emitting diode of the array of light-emitting diodes comprises anupper electrode layer made of an electrically-conductive materialtransparent to the light radiation, the upper electrode layer directlycovering the lateral sidewalls and the upper border of eachlight-emitting diode of the array of light-emitting diodes by being incontact with the upper border of each light-emitting diode of the arrayof light-emitting diodes so as to fill a function of a second electrodecommon to several light-emitting diodes of the array of light-emittingdiodes, the spacing walls directly covering lateral sidewalls and anupper border of the upper electrode layer by being in contact with theupper border of the upper electrode layer and the upper electrode layerbeing in electrical contact with at least one of the light confinementwalls.
 20. The optoelectronic device according to claim 15, wherein thelight confinement walls do not cover the upper border of eachlight-emitting diode of the array of light-emitting diodes and the lightradiation originating from each light-emitting diode of the array oflight-emitting diodes is emitted out of the optoelectronic device by anemission surface of the optoelectronic device located, with respect toeach light-emitting diode of the array of light-emitting diodes, on aside of the upper borders of each light-emitting diode of the array oflight-emitting diodes according to the transverse direction.